Optimistic rollup

An optimistic rollup is a Layer 2 that posts transaction data to Ethereum and assumes batches are valid unless a fraud proof challenges them during a dispute window. Robinhood Chain is an optimistic rollup on the Arbitrum stack. The trade-off is on withdrawals: moving assets out through the canonical bridge waits out the challenge period (seven days on standard Arbitrum rollups) unless a third-party bridge fronts the liquidity.